Slavery was a core fact of life in both Africa and the U.S. during the nineteenth century, profoundly shaping law, politics, society, and ideology. Yet they are rarely compared side by side, a gap that is symptomatic of a larger scholarly disconnection between Africanist and U.S. historians. Drawing on records of court cases and other legal documents, this article compares the southern United States and southern Gold Coast. This limited comparison reveals that claims about key institutions - family and property - were rooted in a complex history of change in the two regions, including internal mass migrations of slaves, the rise of large new slave-based economies, and an intensified focus on kinship as a key component of the masters' ideology of slavery. Masters and slaves struggled over claims to resources - including claims to people - and the social identities that underpinned them. In significant ways, the histories of both regions were shaped by debates about the claims that slaves and their descendants made to kinship and to the products of their labor. Those debates drew substance from - and in turn helped influence - the meanings of property, slavery, and social membership for all people, not just slaves.